1 /* Tree lowering pass. Lowers GIMPLE into unstructured form.
3 Copyright (C) 2003, 2005 Free Software Foundation, Inc.
5 This file is part of GCC.
7 GCC is free software; you can redistribute it and/or modify it under
8 the terms of the GNU General Public License as published by the Free
9 Software Foundation; either version 2, or (at your option) any later
12 GCC is distributed in the hope that it will be useful, but WITHOUT ANY
13 WARRANTY; without even the implied warranty of MERCHANTABILITY or
14 FITNESS FOR A PARTICULAR PURPOSE. See the GNU General Public License
17 You should have received a copy of the GNU General Public License
18 along with GCC; see the file COPYING. If not, write to the Free
19 Software Foundation, 51 Franklin Street, Fifth Floor, Boston, MA
24 #include "coretypes.h"
29 #include "tree-gimple.h"
30 #include "tree-inline.h"
31 #include "diagnostic.h"
32 #include "langhooks.h"
33 #include "langhooks-def.h"
34 #include "tree-flow.h"
42 #include "tree-pass.h"
46 /* Block the current statement belongs to. */
49 /* A TREE_LIST of label and return statements to be moved to the end
51 tree return_statements;
54 static void lower_stmt (tree_stmt_iterator *, struct lower_data *);
55 static void lower_bind_expr (tree_stmt_iterator *, struct lower_data *);
56 static void lower_cond_expr (tree_stmt_iterator *, struct lower_data *);
57 static void lower_return_expr (tree_stmt_iterator *, struct lower_data *);
59 /* Lowers the body of current_function_decl. */
62 lower_function_body (void)
64 struct lower_data data;
65 tree *body_p = &DECL_SAVED_TREE (current_function_decl);
70 gcc_assert (TREE_CODE (bind) == BIND_EXPR);
72 memset (&data, 0, sizeof (data));
73 data.block = DECL_INITIAL (current_function_decl);
74 BLOCK_SUBBLOCKS (data.block) = NULL_TREE;
75 BLOCK_CHAIN (data.block) = NULL_TREE;
76 TREE_ASM_WRITTEN (data.block) = 1;
78 *body_p = alloc_stmt_list ();
79 i = tsi_start (*body_p);
80 tsi_link_after (&i, bind, TSI_NEW_STMT);
81 lower_bind_expr (&i, &data);
83 i = tsi_last (*body_p);
85 /* If the function falls off the end, we need a null return statement.
86 If we've already got one in the return_statements list, we don't
87 need to do anything special. Otherwise build one by hand. */
88 if (block_may_fallthru (*body_p)
89 && (data.return_statements == NULL
90 || TREE_OPERAND (TREE_VALUE (data.return_statements), 0) != NULL))
92 x = build1 (RETURN_EXPR, void_type_node, NULL);
93 SET_EXPR_LOCATION (x, cfun->function_end_locus);
94 tsi_link_after (&i, x, TSI_CONTINUE_LINKING);
97 /* If we lowered any return statements, emit the representative
98 at the end of the function. */
99 for (t = data.return_statements ; t ; t = TREE_CHAIN (t))
101 x = build1 (LABEL_EXPR, void_type_node, TREE_PURPOSE (t));
102 tsi_link_after (&i, x, TSI_CONTINUE_LINKING);
104 /* Remove the line number from the representative return statement.
105 It now fills in for many such returns. Failure to remove this
106 will result in incorrect results for coverage analysis. */
108 #ifdef USE_MAPPED_LOCATION
109 SET_EXPR_LOCATION (x, UNKNOWN_LOCATION);
111 SET_EXPR_LOCUS (x, NULL);
113 tsi_link_after (&i, x, TSI_CONTINUE_LINKING);
116 gcc_assert (data.block == DECL_INITIAL (current_function_decl));
117 BLOCK_SUBBLOCKS (data.block)
118 = blocks_nreverse (BLOCK_SUBBLOCKS (data.block));
120 clear_block_marks (data.block);
123 struct tree_opt_pass pass_lower_cf =
127 lower_function_body, /* execute */
130 0, /* static_pass_number */
132 PROP_gimple_any, /* properties_required */
133 PROP_gimple_lcf, /* properties_provided */
134 PROP_gimple_any, /* properties_destroyed */
135 0, /* todo_flags_start */
136 TODO_dump_func, /* todo_flags_finish */
141 /* Lowers the EXPR. Unlike gimplification the statements are not relowered
142 when they are changed -- if this has to be done, the lowering routine must
143 do it explicitly. DATA is passed through the recursion. */
146 lower_stmt_body (tree expr, struct lower_data *data)
148 tree_stmt_iterator tsi;
150 for (tsi = tsi_start (expr); !tsi_end_p (tsi); )
151 lower_stmt (&tsi, data);
155 /* Lower the OpenMP directive statement pointed by TSI. DATA is
156 passed through the recursion. */
159 lower_omp_directive (tree_stmt_iterator *tsi, struct lower_data *data)
163 stmt = tsi_stmt (*tsi);
165 clause = (TREE_CODE (stmt) >= OMP_PARALLEL && TREE_CODE (stmt) <= OMP_SINGLE)
169 for (; clause; clause = OMP_CLAUSE_CHAIN (clause))
170 TREE_BLOCK (clause) = TREE_BLOCK (stmt);
172 lower_stmt_body (OMP_BODY (stmt), data);
173 tsi_link_before (tsi, stmt, TSI_SAME_STMT);
174 tsi_link_before (tsi, OMP_BODY (stmt), TSI_SAME_STMT);
175 OMP_BODY (stmt) = NULL_TREE;
180 /* Lowers statement TSI. DATA is passed through the recursion. */
183 lower_stmt (tree_stmt_iterator *tsi, struct lower_data *data)
185 tree stmt = tsi_stmt (*tsi);
187 if (EXPR_HAS_LOCATION (stmt) && data)
188 TREE_BLOCK (stmt) = data->block;
190 switch (TREE_CODE (stmt))
193 lower_bind_expr (tsi, data);
196 lower_cond_expr (tsi, data);
199 lower_return_expr (tsi, data);
202 case TRY_FINALLY_EXPR:
204 lower_stmt_body (TREE_OPERAND (stmt, 0), data);
205 lower_stmt_body (TREE_OPERAND (stmt, 1), data);
208 lower_stmt_body (CATCH_BODY (stmt), data);
211 lower_stmt_body (EH_FILTER_FAILURE (stmt), data);
221 case OMP_RETURN_EXPR:
232 lower_omp_directive (tsi, data);
242 /* Lowers a bind_expr TSI. DATA is passed through the recursion. */
245 lower_bind_expr (tree_stmt_iterator *tsi, struct lower_data *data)
247 tree old_block = data->block;
248 tree stmt = tsi_stmt (*tsi);
249 tree new_block = BIND_EXPR_BLOCK (stmt);
253 if (new_block == old_block)
255 /* The outermost block of the original function may not be the
256 outermost statement chain of the gimplified function. So we
257 may see the outermost block just inside the function. */
258 gcc_assert (new_block == DECL_INITIAL (current_function_decl));
263 /* We do not expect to handle duplicate blocks. */
264 gcc_assert (!TREE_ASM_WRITTEN (new_block));
265 TREE_ASM_WRITTEN (new_block) = 1;
267 /* Block tree may get clobbered by inlining. Normally this would
268 be fixed in rest_of_decl_compilation using block notes, but
269 since we are not going to emit them, it is up to us. */
270 BLOCK_CHAIN (new_block) = BLOCK_SUBBLOCKS (old_block);
271 BLOCK_SUBBLOCKS (old_block) = new_block;
272 BLOCK_SUBBLOCKS (new_block) = NULL_TREE;
273 BLOCK_SUPERCONTEXT (new_block) = old_block;
275 data->block = new_block;
279 record_vars (BIND_EXPR_VARS (stmt));
280 lower_stmt_body (BIND_EXPR_BODY (stmt), data);
284 gcc_assert (data->block == new_block);
286 BLOCK_SUBBLOCKS (new_block)
287 = blocks_nreverse (BLOCK_SUBBLOCKS (new_block));
288 data->block = old_block;
291 /* The BIND_EXPR no longer carries any useful information -- kill it. */
292 tsi_link_before (tsi, BIND_EXPR_BODY (stmt), TSI_SAME_STMT);
296 /* Try to determine whether a TRY_CATCH expression can fall through.
297 This is a subroutine of block_may_fallthru. */
300 try_catch_may_fallthru (tree stmt)
302 tree_stmt_iterator i;
304 /* If the TRY block can fall through, the whole TRY_CATCH can
306 if (block_may_fallthru (TREE_OPERAND (stmt, 0)))
309 i = tsi_start (TREE_OPERAND (stmt, 1));
310 switch (TREE_CODE (tsi_stmt (i)))
313 /* We expect to see a sequence of CATCH_EXPR trees, each with a
314 catch expression and a body. The whole TRY_CATCH may fall
315 through iff any of the catch bodies falls through. */
316 for (; !tsi_end_p (i); tsi_next (&i))
318 if (block_may_fallthru (CATCH_BODY (tsi_stmt (i))))
324 /* The exception filter expression only matters if there is an
325 exception. If the exception does not match EH_FILTER_TYPES,
326 we will execute EH_FILTER_FAILURE, and we will fall through
327 if that falls through. If the exception does match
328 EH_FILTER_TYPES, the stack unwinder will continue up the
329 stack, so we will not fall through. We don't know whether we
330 will throw an exception which matches EH_FILTER_TYPES or not,
331 so we just ignore EH_FILTER_TYPES and assume that we might
332 throw an exception which doesn't match. */
333 return block_may_fallthru (EH_FILTER_FAILURE (tsi_stmt (i)));
336 /* This case represents statements to be executed when an
337 exception occurs. Those statements are implicitly followed
338 by a RESX_EXPR to resume execution after the exception. So
339 in this case the TRY_CATCH never falls through. */
344 /* Try to determine if we can fall out of the bottom of BLOCK. This guess
345 need not be 100% accurate; simply be conservative and return true if we
346 don't know. This is used only to avoid stupidly generating extra code.
347 If we're wrong, we'll just delete the extra code later. */
350 block_may_fallthru (tree block)
352 tree stmt = expr_last (block);
354 switch (stmt ? TREE_CODE (stmt) : ERROR_MARK)
359 /* Easy cases. If the last statement of the block implies
360 control transfer, then we can't fall through. */
364 /* If SWITCH_LABELS is set, this is lowered, and represents a
365 branch to a selected label and hence can not fall through.
366 Otherwise SWITCH_BODY is set, and the switch can fall
368 return SWITCH_LABELS (stmt) == NULL_TREE;
371 if (block_may_fallthru (COND_EXPR_THEN (stmt)))
373 return block_may_fallthru (COND_EXPR_ELSE (stmt));
376 return block_may_fallthru (BIND_EXPR_BODY (stmt));
379 return try_catch_may_fallthru (stmt);
381 case TRY_FINALLY_EXPR:
382 /* The finally clause is always executed after the try clause,
383 so if it does not fall through, then the try-finally will not
384 fall through. Otherwise, if the try clause does not fall
385 through, then when the finally clause falls through it will
386 resume execution wherever the try clause was going. So the
387 whole try-finally will only fall through if both the try
388 clause and the finally clause fall through. */
389 return (block_may_fallthru (TREE_OPERAND (stmt, 0))
390 && block_may_fallthru (TREE_OPERAND (stmt, 1)));
393 if (TREE_CODE (TREE_OPERAND (stmt, 1)) == CALL_EXPR)
394 stmt = TREE_OPERAND (stmt, 1);
400 /* Functions that do not return do not fall through. */
401 return (call_expr_flags (stmt) & ECF_NORETURN) == 0;
403 case CLEANUP_POINT_EXPR:
404 return block_may_fallthru (TREE_OPERAND (stmt, 0));
411 /* Lowers a cond_expr TSI. DATA is passed through the recursion. */
414 lower_cond_expr (tree_stmt_iterator *tsi, struct lower_data *data)
416 tree stmt = tsi_stmt (*tsi);
417 bool then_is_goto, else_is_goto;
418 tree then_branch, else_branch;
419 tree then_goto, else_goto;
421 then_branch = COND_EXPR_THEN (stmt);
422 else_branch = COND_EXPR_ELSE (stmt);
424 lower_stmt_body (then_branch, data);
425 lower_stmt_body (else_branch, data);
427 then_goto = expr_only (then_branch);
428 then_is_goto = then_goto && simple_goto_p (then_goto);
430 else_goto = expr_only (else_branch);
431 else_is_goto = else_goto && simple_goto_p (else_goto);
433 if (!then_is_goto || !else_is_goto)
435 tree then_label, else_label, end_label, t;
437 then_label = NULL_TREE;
438 else_label = NULL_TREE;
439 end_label = NULL_TREE;
441 /* Replace the cond_expr with explicit gotos. */
444 t = build1 (LABEL_EXPR, void_type_node, NULL_TREE);
445 if (TREE_SIDE_EFFECTS (then_branch))
449 then_goto = build_and_jump (&LABEL_EXPR_LABEL (t));
454 t = build1 (LABEL_EXPR, void_type_node, NULL_TREE);
455 if (TREE_SIDE_EFFECTS (else_branch))
459 /* Both THEN and ELSE can be no-ops if one or both contained an
460 empty BIND_EXPR that was associated with the toplevel block
461 of an inlined function. In that case remove_useless_stmts
462 can't have cleaned things up for us; kill the whole
472 else_goto = build_and_jump (&LABEL_EXPR_LABEL (t));
477 bool may_fallthru = block_may_fallthru (then_branch);
479 tsi_link_after (tsi, then_label, TSI_CONTINUE_LINKING);
480 tsi_link_after (tsi, then_branch, TSI_CONTINUE_LINKING);
482 if (else_label && may_fallthru)
484 end_label = build1 (LABEL_EXPR, void_type_node, NULL_TREE);
485 t = build_and_jump (&LABEL_EXPR_LABEL (end_label));
486 tsi_link_after (tsi, t, TSI_CONTINUE_LINKING);
492 tsi_link_after (tsi, else_label, TSI_CONTINUE_LINKING);
493 tsi_link_after (tsi, else_branch, TSI_CONTINUE_LINKING);
497 tsi_link_after (tsi, end_label, TSI_CONTINUE_LINKING);
500 COND_EXPR_THEN (stmt) = then_goto;
501 COND_EXPR_ELSE (stmt) = else_goto;
507 lower_return_expr (tree_stmt_iterator *tsi, struct lower_data *data)
509 tree stmt = tsi_stmt (*tsi);
510 tree value, t, label;
512 /* Extract the value being returned. */
513 value = TREE_OPERAND (stmt, 0);
514 if (value && TREE_CODE (value) == MODIFY_EXPR)
515 value = TREE_OPERAND (value, 1);
517 /* Match this up with an existing return statement that's been created. */
518 for (t = data->return_statements; t ; t = TREE_CHAIN (t))
520 tree tvalue = TREE_OPERAND (TREE_VALUE (t), 0);
521 if (tvalue && TREE_CODE (tvalue) == MODIFY_EXPR)
522 tvalue = TREE_OPERAND (tvalue, 1);
526 label = TREE_PURPOSE (t);
531 /* Not found. Create a new label and record the return statement. */
532 label = create_artificial_label ();
533 data->return_statements = tree_cons (label, stmt, data->return_statements);
535 /* Generate a goto statement and remove the return statement. */
537 t = build1 (GOTO_EXPR, void_type_node, label);
538 SET_EXPR_LOCUS (t, EXPR_LOCUS (stmt));
539 tsi_link_before (tsi, t, TSI_SAME_STMT);
544 /* Record the variables in VARS into function FN. */
547 record_vars_into (tree vars, tree fn)
549 struct function *saved_cfun = cfun;
551 if (fn != current_function_decl)
552 cfun = DECL_STRUCT_FUNCTION (fn);
554 for (; vars; vars = TREE_CHAIN (vars))
558 /* BIND_EXPRs contains also function/type/constant declarations
559 we don't need to care about. */
560 if (TREE_CODE (var) != VAR_DECL)
563 /* Nothing to do in this case. */
564 if (DECL_EXTERNAL (var))
567 /* Record the variable. */
568 cfun->unexpanded_var_list = tree_cons (NULL_TREE, var,
569 cfun->unexpanded_var_list);
572 if (fn != current_function_decl)
577 /* Record the variables in VARS into current_function_decl. */
580 record_vars (tree vars)
582 record_vars_into (vars, current_function_decl);
586 /* Mark BLOCK used if it has a used variable in it, then recurse over its
590 mark_blocks_with_used_vars (tree block)
595 if (!TREE_USED (block))
597 for (var = BLOCK_VARS (block);
599 var = TREE_CHAIN (var))
603 TREE_USED (block) = true;
608 for (subblock = BLOCK_SUBBLOCKS (block);
610 subblock = BLOCK_CHAIN (subblock))
611 mark_blocks_with_used_vars (subblock);
614 /* Mark the used attribute on blocks correctly. */
617 mark_used_blocks (void)
619 mark_blocks_with_used_vars (DECL_INITIAL (current_function_decl));
623 struct tree_opt_pass pass_mark_used_blocks =
627 mark_used_blocks, /* execute */
630 0, /* static_pass_number */
632 0, /* properties_required */
633 0, /* properties_provided */
634 0, /* properties_destroyed */
635 0, /* todo_flags_start */
636 TODO_dump_func, /* todo_flags_finish */